<?php

/**
 * Google Authenticator Library Class
 *
 * @author   SharkIng <SharkIng@Shacas.com>
 */

/*
|--------------------------------------------------------------------------
| PHP Class for handing Google Autheticator 2-factor authentication
|--------------------------------------------------------------------------
|
*/

class GoogleAuth
{

	protected $_codeLength = 6;

	/**
	 * Get array with all 32 characters for decoding from/encoding to base32
	 * 
	 * @return array
	 * @copyright 2012 Michael Kliewe
	 */
	protected function _getBase32LookupTable()
	{
		return array(
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', //  7
            'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
            'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
            '='  // padding char			
		);
	}

	/**
	 * Encode base32
	 * 
	 * @param  string  $secret
	 * @param  boolean $padding
	 * @return string
	 *
	 * @copyright 2012 Michael Kliewe
	 */
	protected function _base32Encode($secret, $padding = true)
	{
		if (empty($secret))
		{
			return '';
		}

		$base32chars = $this -> _getBase32LookupTable();

		$secret = str_split($secret);

        $binaryString = "";
        
        for ($i = 0; $i < count($secret); $i++) 
        {
            $binaryString .= str_pad(base_convert(ord($secret[$i]), 10, 2), 8, '0', STR_PAD_LEFT);
        }
        
        $fiveBitBinaryArray = str_split($binaryString, 5);
        $base32 = "";
        $i = 0;
        
        while ($i < count($fiveBitBinaryArray)) 
        {
            $base32 .= $base32chars[base_convert(str_pad($fiveBitBinaryArray[$i], 5, '0'), 2, 10)];
            $i++;
        }
        
        if ($padding && ($x = strlen($binaryString) % 40) != 0) 
        {
            if ($x == 8) $base32 .= str_repeat($base32chars[32], 6);
            elseif ($x == 16) $base32 .= str_repeat($base32chars[32], 4);
            elseif ($x == 24) $base32 .= str_repeat($base32chars[32], 3);
            elseif ($x == 32) $base32 .= $base32chars[32];
        }
        
        return $base32;
	}


    /**
     * Decode base32
     *
     * @param $secret
     * @return bool|string
     *
     * @copyright 2012 Michael Kliewe
     */
    protected function _base32Decode($secret)
    {
        if (empty($secret))
        {
        	return '';
        }

        $base32chars = $this->_getBase32LookupTable();
        
        $base32charsFlipped = array_flip($base32chars);
        
        $paddingCharCount = substr_count($secret, $base32chars[32]);
        
        $allowedValues = array(6, 4, 3, 1, 0);
        
        if (!in_array($paddingCharCount, $allowedValues))
        {
        	return false;
        }
        
        for ($i = 0; $i < 4; $i++)
        {
            if ($paddingCharCount == $allowedValues[$i] &&
                substr($secret, -($allowedValues[$i])) != str_repeat($base32chars[32], $allowedValues[$i])) 
                {
                	return false;
                }
        }
        
        $secret = str_replace('=','', $secret);
        $secret = str_split($secret);
        $binaryString = "";
        
        for ($i = 0; $i < count($secret); $i = $i+8) 
        {
            $x = "";
            if (!in_array($secret[$i], $base32chars))
            {
            	return false;
            }
            
            for ($j = 0; $j < 8; $j++) 
            {
                $x .= str_pad(base_convert(@$base32charsFlipped[@$secret[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
            }
            
            $eightBits = str_split($x, 8);
            
            for ($z = 0; $z < count($eightBits); $z++) 
            {
                $binaryString .= ( ($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48 ) ? $y:"";
            }
        }
        
        return $binaryString;
    }

    /**
     * Using Google QR Code Gen to get QR Code Image
     * @param  string $name   
     * @param  string $secret 
     * @return string
     */
	public function createQRCode ($name, $secret)
	{
		//$urlencoded = urlencode('otpauth://totp/'.$name.'?secret='.$secret.'');
		//return 'https://chart.googleapis.com/chart?chs=200x200&chld=M|0&cht=qr&chl='.$urlencoded.'';
		
		return 'otpauth://totp/'.$name.'?secret='.$secret.'';
	}

	/**
	 * Ceate new secret. 16 random characters from base32 table
	 * 
	 * @return string
	 */
	public function createSecret ()
	{
		$validChars = $this -> _getBase32LookupTable();

		unset($validChars[32]);
        
        $secret = '';
        
        for ($i = 0; $i < 16; $i++) {
            $secret .= $validChars[array_rand($validChars)];
        }

        return $secret;
	}

    /**
     * Calculate the code, with given secret and point in time
     *
     * @param string $secret
     * @param int|null $timeSlice
     * @return string
     *
     * @copyright 2012 Michael Kliewe
     */
    public function createCode($secret, $timeSlice = null)
    {
        if ($timeSlice === null) {
            $timeSlice = floor(time() / 30);
        }
        
        $secretkey = $this->_base32Decode($secret);
        // Pack time into binary string
        $time = chr(0).chr(0).chr(0).chr(0).pack('N*', $timeSlice);
        // Hash it with users secret key
        $hm = hash_hmac('SHA1', $time, $secretkey, true);
        // Use last nipple of result as index/offset
        $offset = ord(substr($hm, -1)) & 0x0F;
        // grab 4 bytes of the result
        $hashpart = substr($hm, $offset, 4);
        // Unpak binary value
        $value = unpack('N', $hashpart);
        $value = $value[1];
        // Only 32 bits
        $value = $value & 0x7FFFFFFF;
        $modulo = pow(10, $this->_codeLength);
        return str_pad($value % $modulo, $this->_codeLength, '0', STR_PAD_LEFT);
    }

    /**
     * Check if the code is correct. This will accept codes starting from $discrepancy*30sec ago to $discrepancy*30sec from now
     *
     * @param string $secret
     * @param string $code
     * @param int $discrepancy This is the allowed time drift in 30 second units (8 means 4 minutes before or after)
     * @param int|null $currentTimeSlice time slice if we want use other that time()
     * @return bool
     *
     * @copyright 2012 Michael Kliewe
     */
    public function verifyCode($secret, $code, $discrepancy = 1, $currentTimeSlice = null)
    {
        if ($currentTimeSlice === null) {
            $currentTimeSlice = floor(time() / 30);
        }
        for ($i = -$discrepancy; $i <= $discrepancy; $i++) {
            $calculatedCode = $this->createCode($secret, $currentTimeSlice + $i);
            if ($calculatedCode == $code ) {
                return true;
            }
        }
        return false;
    }

}